Newsgroups: comp.arch
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: ieee floating standard
Message-ID: <1991May22.235155.7807@zoo.toronto.edu>
Date: Wed, 22 May 1991 23:51:55 GMT
References: <9105220041.AA14355@ucbvax.Berkeley.EDU> <1991May22.221824.16887@riacs.edu>
Organization: U of Toronto Zoology

In article <1991May22.221824.16887@riacs.edu> lamaster@pioneer.arc.nasa.gov (Hugh LaMaster) writes:
>The down side of IEEE is a performance hit in heavily pipelined FP units, for
>some input values...

Of note in this connection is the AMD 29050's "sloppy" mode.  (Well, they
don't call it that. :-))  This treats all denormalized numbers as zero,
and generates a zero whenever you would normally get a denormalized number.
So the user gets a choice:  if he really wants the highest possible speed,
or highly predictable speed without data-dependent delays, he can turn on
sloppy mode.  On the other hand, if he merely wants the right answer :-),
he can use IEEE-standard arithmetic.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry